A Study of Rebif® Compared With Avonex® in the Treatment of Relapsing-remitting Multiple Sclerosis (MS)

Inclusion Criteria: Age between 18 and 55 years Clinically definite or laboratory-supported definite relapsing-remitting MS according to Poser's criteria Two or more relapses within the preceding 24 months Clinical stability or improving neurological state during the 4 weeks before Study Day 1 Expanded disability status scale (EDSS) score from 0 to 5.5, inclusive Two or more lesions consistent with MS on a Screening proton density/T2-magnetic resonance imaging (MRI) scan to be performed 28 plus/minus (+/-) 4 days before the Study Day 1 MRI Willingness and ability to comply with the protocol for the duration of the study Written informed consent given before any study-related procedure not part of the subject's normal medical care, with the understanding that the subject can withdraw consent at any time without prejudice to future medical care For female subjects, lack of childbearing potential must be satisfied by either being post-menopausal or surgically sterilized or using a hormonal contraceptive, intra-uterine device, diaphragm with spermicide or condom with spermicide for the duration of the study. Subjects should neither be pregnant nor breast-feeding; confirmation that the subject is not pregnant will be established by a negative serum human chorionic gonadotropin (hCG) pregnancy test within 7 days of Study Day 1 (the pregnancy test will not be required of subjects who will be post-menopausal or surgically sterilized) Exclusion Criteria: Secondary progressive MS, primary progressive MS or progressive relapsing MS Prior use of interferon Treatment with oral or systemic corticosteroids or adrenocorticotropic hormone (ACTH) within 4 weeks of Study Day 1 or within 7 days before the Screening MRI Psychiatric disorder that is unstable or will preclude safe participation in the study Significant leucopenia (white blood cell count less than 0.5 times the lower limit of normal) within 7 days of Study Day 1 Elevated liver function tests (Alanine transaminase [ALT], Aspartate transaminase [AST], alkaline phosphatase or total bilirubin greater than 2 times the upper limit of normal) within 7 days of Study Day 1 Prior cytokine or anti-cytokine therapy or glatiramer acetate within the 3 months before Study Day 1 Immunomodulatory or immunosuppressive therapy within the 12 months before Study Day 1, including but not limited to cyclophosphamide, cyclosporin, methotrexate, azathioprine, linomide and mitoxantrone Previous use of cladribine or total lymphoid irradiation Allergy to human serum albumin, mannitol or gadolinium diethylenetriaminepentacetic acid (DTPA) Intravenous immunoglobulin or any other investigational drug or procedure in the 6 months before Study Day 1 Systemic disease that can interfere with subject safety, compliance or evaluation of the condition under study, such as insulin-dependent diabetes, Lyme disease, clinically significant cardiac disease or infection with human immunodeficiency virus (HIV) or Human T-cell lymphotrophic virus, Type-1 (HTLV-1)